Mold liner



March 6, 1962 A. o. HORD ET AL MOLD LINER 2 Sheets-Sheet 1 Filed Dec. 2,1959 1 H h M INVENTORS. E O. HORD 8 N G. ROYAL ATTORNEY.

ALSI BY JOH 7 March 6, 1962 A. o. HORD ET AL 3,023,468

MOLD LINER Filed Dec. 2, 1959 v 2 Sheets-Sheet 2 IN V EN TORS.

ALSIE o. HORD & BY JOHN G. ROYAL ATTORNEY.

w wwwv 3,023,468 MOLD LINER Aisie 0. Hard, Greentown, and John G. Royal,Kokomo,

Ind., assignors to Union Carbide Corporation, a corporation of New YorkFiled Dec. 2, 1959, Ser. No. 856,819 7 Claims. (Cl. 22-116) Thisinvention relates to mold liners used in the production of ingots and toa method for producing ingots of an improved quality.

The casting of metals into forms and, in particular, ingots is oftenonly the first step in the fabrication of other more complex shapes. Itis, therefore, often essential that these ingots be of a high degree ofquality. In particular, the surface of the ingot must be free of thosesurface imperfections which interfere with forging, rolling, drawing orother forming operations.

In practice ingots are produced having surface defects such as scabs,pits, blowholes, inclusions, etc., which must be removed by grinding,machining, scarfing, etc., before a surface satisfactory for formingoperations is presented. These expensive finishing operations, whichalso decrease the yield of useful metals obtained from an ingot, arenecessary lest the surface defects be carried over into the fabricatedarticle.

To prevent the formation of these surface defects in castings and ingotsand thereby do away with the expensive finishing operations, variousmold liners and coatings 'have been used. For example, metallic andnon-metallic materials have been used as liners or curtains to preventthe splashing and surging of molten metal on the ingot mold wall.

The use of consumable non-metallic materials as coatings or linings astaught by the prior art has several inherent disadvantages. For example,the material may either melt or flake off into the cast molten metal andbecome embedded therein as a non-metallic inclusion or the heat of themolten metal may decompose the coating or lining material and therebyintroduce harmful products of decomposition into the molten metal.

Molds have been lined in the past with non-consumable,

non-metallic materials but the results were not satisfactory. Previousattempts to use heat-resistant materials and, in particular, asbestossheet, as mold liners were not successful. When an asbestos liner isloosely fitted into a mold, it buckles and folds, entrapping metalWithin the folds. When an asbestos liner is rigidly fixed to the moldwalls, it tears under the pressure of the surging molten metal, leavingunprotected areas and introducing asbestos into the metal.

It is the primary object of this invention therefore to provide aprocess for casting ingots having a surface which is substantially freefrom imperfections.

It is also an object of this invention to provide an im proved moldlining consisting of sheets of an asbestos material for use in producingingots having a surface free of imperfections.

It is another object of this invention to provide a process for castingingots substantially free from surface defects and internal defects.

It is also an object of this invention to provide a process for castingingots which give a greater yield and quality of fabricated productafter forging, rolling or drawing of the ingot.

3,023,468 Patented Mar. 6, 1962 ice It is a further object of thisinvention to provide a mold liner Which protects the inner surface ofthe ingot mold, and makes easier the removal of the ingot from the moldand also extends the life of the mold.

Other aims and advantages of this invention will be apparent from thefollowing description and the appended claims.

In accordance with the present invention a method for casting metals isprovided comprising lining the mold with at least one sheet ofheat-resistant material, said sheet having sufiicient rigidity tosupport itself vertically when positioned snugly within the mold as aliner having substantially the same configuration as the configurationof the mold, the longitudinal edges of said sheet overlapping oneanother, means for preventing buckling of the liner during pouring ofthe molten metal, said means permitting movement of the overlapped edgesof said sheets relative to each other to permit expansion of said linerduring pouring, pouring molten metal into the solined mold, whereby thepressure of the molten metal causes the lining to arrange itself againstthe walls of the mold, and then solidifying the molten metal in themold.

in the drawings:

FIG. 1 is an elevational sectional view of an ingot mold lined inaccordance with the invention;

FIG. 2 is an isometric view of the S-shaped retaining clip;

FIG. 3 is a fragmentary detail of FIG. 1 before pour- 7 ing molten metalinto the lined mold and;

FIG. 4 is a fragmentary detail of FIG. 1 after pouring molten metal intothe lined mold;

FIG. 5 is a section taken along the line 55 of FIG. 1;

FIG. 6 is the elevational sectional view of FIG. 1 while metal is beingpoured.

In FIGURE 1 an upright ingot mold 11 is shown containing an assembledliner 12. composed of two asbestos sheets 13 and 14 fitted snugly in themold. The longitudinal edges of the sheets are overlapped and heldtogether by the S-shaped clips 15. Vents 16 for the escape of air andgases are also shown. The upper end 17 of the liner is shown extendingto a point about one inch short of the top of the upright mold.

FIGURE 2 shows the S-shaped clip which holds the longitudinal edges ofthe sheets in an overlapped relationship and allows the asbestos sheetto support itself when positioned in the mold and which simultaneouslyallows the liner to expand with the pressure of the molten metal duringpouring. The S-shaped clip can be formed from a strip of resilientmaterial by bending the strip twice, i.e.., by bending the strip back onitself twice. The clip thus formed has three legs 18, 19, and 20 formingtwo oppositely disposed openings, 21 and 22, into which the longitudinaledges of the asbestos sheet are inserted. The clip should besufficiently resilient to slidably grip the edges of the sheets. Thewidth of these openings is determined by the thickness of the asbestossheet material being used. The width is regulated to permit the asbestossheet to slide out of the clip when pulled. The length of the clipopening should be sufficient to prevent buckling of the sheet whenformed into an upright standing envelope. The number of clips requiredis similarly related to the size of the envelope and should besufiicient to allow the envelope to stand upright in the empty moldwithout buckling.

In FIG. 6 a pouring of metal into the asbestos lined ingot mold isshown. The asbestos liner is shown fitted in the mold somewhat looselyfor the purposes of explanation but it is actually fitted snugly in themold. As the mold fills with molten metal 25 the pressure of the metalforces the asbestos liner to expand outward, arranging itself againstthe walls of the ingot mold. Before pouring of the metal as shown inFIG. 3, each S-shaped clip 15 holds the edges of the asbestos sheets 13and 14 in an overlapping relationship. During pouring the circumferenceof the liner lengthens as the liner is pushed outward to the mold walls.The increase in liner circumference is made up by the movement of theends of the sheet sliding out of the S-shaped clips. After pouring theclips still hold the edges of the asbestos liner in an overlappingrelationship but, as seen in FiG. 4, the edges have moved relative toeach other to provide an increased liner circumference.

Whereas loosely fitted or rigidly fitted sheets are not able to resistthe forces of the surging molten metal, a liner fitted and arrangedaccording to the method of this invention is able to accommodate itselfto the forces and pressures exerted by the molten metal. By insertingthe liner in the mold snugly, i.e, tightly yet free to yield whenstrained, and arranging it with the longitudinal edges overlapped butfree to move, the liner is free to position itself against the walls ofthe mold when the metal is poured.

Any means for preventing the liner from buckling while permitting theoverlapped longitudinal edges to move is suitable. The preferred meansis a fastener holding the longitudinal edges together while permittingthem to move, but other means for accomplishing the same result areincluded within the scope of this invention.

One example of the preferred means is the S-shaped clip described above.Any other type fastener which will hold the longitudinal edges in anoverlapped relationship while permitting the edges to withdraw from therestraint of the fastener when stressed, thereby allowing expansion ofthe liner, is suitable.

in an example of the practice of the invention an openended ingot moldhaving a tapered mold cavity is lined using two sheets of asbestosmaterial by first positioning the mold on its side as in FIG. andinserting therein a sheet 13 of asbestos material. The sheet should beat least equal in length to the depth of the mold and should be slightlywider than one-half the circumference of the mold so as to provide anoverlapping area when a second, similarly-sized sheet 14 is inserted inthe mold.

The first sheet is smoothed in place against the walls of the mold tomake a snug fit. A number of S-shaped clips 15 are inserted over onelongitudinal edge of the sheet 13 ready to receive the edges of thesecond sheet 14 when it is inserted in the mold. The other longitudinaledge of the first sheet 13 is fitted with a number of unformed clips 23having a hook-like configuration. When the second sheet is inserted inthe mold, one edge is inserted into the clips 15 and the sheet issmoothed against the walls of the mold opposite the first sheet with anoverlap on the first sheet of about 2 inches. The other edge of thesecond sheet overlaps the first sheet and is secured in position bybending the free end of the unforrned clip 23 over it. When the liner isthus fashioned, the operator may then pull the ends of the liner throughthe opening at the small end of the tapered mold to fit the liner snuglyinto place. This movement of the liner should leave a bare ring at thetop of the mold 17.

The practice of bending the unformed clip into its 8- shape within themold, rather than before the sheets are inserted in the mold, has beenfound to give a more secure fit. However, both sets of clips may be bentto the prescribed S-shape before the liner is assembled.

The S-shaped clips may be formed from blanks of a resilient material,such as steel, having a length of about 5 inches and a width of aboutone-half inch, although other sizes may be used. A mold about 40 inchesin depth would require from about 4 to about 8 clips evenly spaced alongeach longitudinal edge.

Molds of any cross-sectional configuration may be fitted with theasbestos lining described above. The asbestos sheets are merely formedor bent into a lining having a configuration similar to that of the moldwith the overlapping ends held by the S-shaped clips described above. Inthis way circular, oval, square, hexagonal and any other type mold maybe provided with the asbestos liner of this invention. Any number ofsheets may be used to form the liners. One sheet may be used with itsedges overlapping or two or more sheets may be connected edge to edgewith the S-shaped clips depending on the size and configuration of themold.

Furthermore, pigs or semi-finished articles may be cast in molds linedwith asbestos sheets in the manner of this invention. The onlyrequirement is that the mold be of a simple shape allowing the use ofthe asbestos sheet material which is held free to arrange itself againstthe walls of the mold when stressed by the pressure of the molten metal.

The lining material may be made of asbestos paper sheet or asbestostextiled fabric within the range of from about -inch thick to about%-inch thick. Good results have been obtained using a i -inch thickasbestos paper sheet having the chemical analysis shown in Table 1.

TABLE 1 Chemical Analysis of Asbestos Paper Sheet Other materials loston ignition at 1000-" C.,

1 hr. Balance The balance or 19.69 percent of the material is made up ofconsumable materials such as starch or other binders and water. Thewater content was found to be 14.95 percent at 800 C.

When molten metal is poured into the lined mold, its heat causes thevaporization of the water and starch contained in the asbestos and theWater in the ingot mold walls. The resulting steam causes undesirableagitation of the metal and can cause explosive rupture of the liner. Theasbestos-lined mold should preferably be preheated to drive off thiswater. However, the venting system described below will allow for theescape of any such water if preheating of the mold is not practiced oris incomplete.

Other materials than asbestos may be used for the liner provided theyare heatresistant, i.e., are not consumable by the heat of the moltenmetal.

One of the most important benefits obtained from the use of aheat-resistant liner such as an asbestos liner in an ingot mold is thecontrol of the metal droplets as they are splashed upward during thepouring operation as shown in FIG. 6. The metal droplets 24 strike theasbestos sheet 14 and fall back and are incorporated into the liquidmetal 25. The insulating effect of the asbestos sheet prevents thesudden chilling and freezing of the droplets. This, of course, preventsthe formation of those defects commonly found on the surface of as-castingots as a result of the freezing of metal splashings. If no liner isused, or if a metal liner is used, these droplets freeze on the walls ofthe mold or metal liner and cause the above-described defects on thesurface of the ingot. Similarly, if a lining formed of a glass-likecoating on the walls of the mold is used, the hot metal droplets eitherfuse to the lining and freeze or they melt the lining causing thedroplet and glass coating to fall back into the melt. These glassfragments can cause undesirable inclusions in the ingot. However, theingots cast in an asbestos-lined mold are free of these and otherdefects, e.g., scabs, cold shuts, blowholes, inclusions, pits andgenerally rough surface.

The asbestos liner also serves to insulate the ingot from the mold wallsthereby providing for a less rapid cooling and solidification of theingot.

The use of an asbestos liner also results in easier removal of the ingotfrom the mold. The walls of the mold are less subject to attack from thehot metal and therefore give a longer useful life.

In FIG. 6 the escape path of accumulated gas or air is shown. Thesegases form when the molten metal vaporizes the water contained in theasbestos liner and mold walls. Any gas or air entrapped between themolten metal and the liner is forced through the vents 16 into the space26 between the liner and the mold walls. As the level of the moltenmetal rises, it forces any air or gas entrapped in the space between themold walls and the liner to flow upward and out through the vents intothe mold cavity (as shown by the arrows). The liner should preferablynot extend all the way to the top of the mold but rather should fallshort of 17 by about one, inch. This arrangement has been found to alloweasy escape of the gases.

The vents described above may be perforations ranging from about ;4;-inch to about %-inch or over in diameter and the number of perforationsmay vary from about one per square foot to over 20 per square footdepending on the amount of moisture which may be vaporized. An optimumarrangement consists of about sixteen 43- inch diameter perforations persquare foot.

These perforations may be made with a sharp tool by merely pushing ahole through the asbestos and pushing the flap up to leave a hole ormore preferably by punching out a portion of the asbestos to make theperforations. The vents need not be actual perforations, moreover, butmay be the natural openings found in woven materials such as an asbestoswoven fabric. Therefore, a woven asbestos fabric may be used withoutvents provided the weave is coarse enough to permit venting of thegases.

The use of the asbestos mold liner of this invention results insubstantial economic savings through the elimination of the need forextensive surface grinding operations. Furthermore, there is anincreased yield of usable producton the average of a 5 percent increase.Asbestos liners fashioned in the manner described in the example andhaving a composition such as that given in Table 1 have been usedsuccessfully to cast ingots of cobalt-base, nickel-base, and iron-basealloys. These ingots were substantially free of surface defects.

The description of this invention has been in terms of its specificembodiments. Modifications and equiv alents will be apparent to thoseskilled in the art and this disclosure is intended to be illustrativeof, but not necessarily to constitute a limitation upon the scope of theinvention.

It is to be understood that the language in the foregoing claimspertaining to ingot molds not only includes molds having a circularcross-section, as shown in the accompanying figures, but also includesmolds having other geometrical configurations such as square, hexagonal,rectangular, octagonal, oval, and slab molds.

What is claimed is:

l. A composite mold for the casting of metals comprising, incombination, a mold having a cavity to receive molten metal, and anasbestos liner snugly fitted along the walls of said cavity, said linerconsisting of at least one sheet of an asbestos material, thelongitudinal edges of said sheets overlapping one another, movementpermitting rneans holding said edges overlapped for preventing bucklingof the liner during pouring of the metal, said means maintaining thelongitudinal edges of said sheets in an overlapped relationship andpermitting movement of the overlapped edges of said sheets relative toeach other to permit expansion of the liner during pouring of moltenmetal into the so-lined mold.

2. A composite mold for the casting of metals comprising, incombination, a mold having a cavity to receive molten metal, an asbestosliner snugly fitted along the walls of said cavity, said linerconsisting of at least one sheet of an asbestos material, said asbestosmaterial having vents to permit the passage of gases therethrough, thelongitudinal edges of said sheets overlapping one another, slidablefastening means interconnecting said overlapped edges, said meansmaintaining the longitudinal edges in overlapped relationship andpermitting the movement of the overlapped edges relative to each otherto permit expansion of the liner during pouring of molten metal into theso-lined mold.

3. A composite mold for casting of metals comprising, in combination, amold having a cavity to receive molten metal, an asbestos liner snuglyfitted along the walls of said cavity, said liner consisting of at leastone sheet of an asbestos material, said sheets having perforations topermit the passage of gases therethrough, the longitudinal edges of saidsheets overlapping one another, a plurality of generally S-shaped clipsinserted over said longitudinal overlapped edges to maintain said edgesin an overlapped relationship and to permit expansion of said linerduring pouring of the molten metal into the so-lined mold.

4. A mold liner for use in a mold in the casting of etals comprising, incombination, at least one sheet of an asbestos material arranged into anopen-ended body having substantially the same configuration as theconfiguration of a mold, the longitudinal edges of said sheetsoverlapping one another sufiiciently to prevent parting of said sheetsand exposure of a mold wall to molten metal when poured, a plurality ofgenerally S-shaped clips having two oppositely disposed openings, theoverlapping edges of said sheets inserted in the openings in the clips.

5. In the method of casting metal in an ingot mold, the improvementcomprising arranging at least one sheet of heat-resistant materialsnugly within the mold with the longitudinal edges overlapping oneanother but free to move relative to each other, preventing buckling ofthe liner during pouring of the molten metal by attaching means formaintaining the edges of said sheets overlapped but free to moverelative to each other to permit expansion of said liner during pouring,pouring molten metal into the so-lined mold, whereby the pressure of themolten metal causes the liner to arrange itself against the walls of themold, and then solidifying the molten metal in the mold.

6. In the method of casting metal in an ingot mold, the improvementcomprising arranging at least one sheet of an asbestos material snuglywithin the mold with longitudinal edges of said sheets overlapping oneanother but free to move relative to each other, said asbestos materialhaving perforations to permit the passage therethrough of gases, saidsheets having sufiicient rigidity to support themselves vertically whenpositioned snugly within the mold as a liner having substantially thesame configuration as the configuration of the mold, preventing bucklingof the liner during pouring of the molten metal by attaching means formaintaining the edges of said sheets in an overlapped relationship butfree to move relative to each other to permit expansion of the linerduring pouring, said edges overlapping sufficiently to prevent partingof the edges and exposure of the mold Walls to the molten metal whenpoured, pouring molten metal into the solined mold, whereby the pressureof the molten metal causes the liner to arrange itself against the wallsof the mold, and then solidifying the molten metal in the mold.

7. In the method of casting metal in an ingot mold, the improvementcomprising arranging at least one sheet of an asbestos material snuglywithin the mold with the longitudinal edges of said sheet overlappingone another but free to move relative to each other, said asbestosmaterial having perforations to permit the passage therethrough ofgases, preventing buckling of the liner during pouring by attaching aplurality of generally S-shaped clips over the overlapped edges of saidsheet at substantially even-spaced intervals for maintaining the edgesof said sheets in an overlapped relationship but free to slide relativeto each other to permit expansion of the liner during pouring, saidedges overlapping sufficiently to prevent parting of the edges andexposure of the mold Walls to the molten metal when poured, pouringmetal in the so-lined mold, whereby the pressure of the molten metalcauses the liner to arrange itself against the walls of the mold andthen solidi: tying the molten metal in the mold.

References Cited in the file of this patent UNITED STATES PATENTS FosterMar. 24, 1903 Woodruff Jan. 5, 1915 Crowther May 24, 1932 Terrill Feb.17, 1942 Olsen Jan. 10, 1950 Olsen Aug. 8, 1950 Grant Sept. 18, 1956

